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[PATCH 2/2] Add VDSO version of sched_getcpu on powerpc


The kernel patch has been submitted and is in the review process.
Results on a POWER7 show the speedup of a sched_getcpu call:

baseline: 538 cycles 
vdso:      30 cycles

2012-07-09  Anton Blanchard  <anton@samba.org>

	* sysdeps/unix/sysv/linux/powerpc/sched_getcpu.c: New file.
	* sysdeps/unix/sysv/linux/powerpc/Versions: Add __vdso_getcpu
	* sysdeps/unix/sysv/linux/powerpc/bits/libc-vdso.h: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/init-first.c: Likewise.

---
 sysdeps/unix/sysv/linux/powerpc/sched_getcpu.c   |   30 +++++++++++++++++++++++
 sysdeps/unix/sysv/linux/powerpc/Versions         |    1 
 sysdeps/unix/sysv/linux/powerpc/bits/libc-vdso.h |    2 +
 sysdeps/unix/sysv/linux/powerpc/init-first.c     |    3 ++
 4 files changed, 36 insertions(+)

Index: glibc/sysdeps/unix/sysv/linux/powerpc/sched_getcpu.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ glibc/sysdeps/unix/sysv/linux/powerpc/sched_getcpu.c	2012-06-25 09:44:20.067041483 +1000
@@ -0,0 +1,30 @@
+/* Copyright (C) 2012 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <sched.h>
+#include <sysdep.h>
+#include <bits/libc-vdso.h>
+
+
+int
+sched_getcpu (void)
+{
+  unsigned int cpu;
+  int r = INLINE_VSYSCALL (getcpu, 3, &cpu, NULL, NULL);
+
+  return r == -1 ? r : cpu;
+}
Index: glibc/sysdeps/unix/sysv/linux/powerpc/Versions
===================================================================
--- glibc.orig/sysdeps/unix/sysv/linux/powerpc/Versions	2012-06-25 09:42:38.000000000 +1000
+++ glibc/sysdeps/unix/sysv/linux/powerpc/Versions	2012-06-25 09:44:20.067041483 +1000
@@ -3,5 +3,6 @@ libc {
     __vdso_get_tbfreq;
     __vdso_clock_gettime;
     __vdso_clock_getres;
+    __vdso_getcpu;
   }
 }
Index: glibc/sysdeps/unix/sysv/linux/powerpc/bits/libc-vdso.h
===================================================================
--- glibc.orig/sysdeps/unix/sysv/linux/powerpc/bits/libc-vdso.h	2012-06-25 09:42:38.000000000 +1000
+++ glibc/sysdeps/unix/sysv/linux/powerpc/bits/libc-vdso.h	2012-06-25 09:44:20.067041483 +1000
@@ -30,6 +30,8 @@ extern void *__vdso_clock_getres;
 
 extern void *__vdso_get_tbfreq;
 
+extern void *__vdso_getcpu;
+
 #endif
 
 #endif /* _LIBC_VDSO_H */
Index: glibc/sysdeps/unix/sysv/linux/powerpc/init-first.c
===================================================================
--- glibc.orig/sysdeps/unix/sysv/linux/powerpc/init-first.c	2012-06-25 09:43:43.000000000 +1000
+++ glibc/sysdeps/unix/sysv/linux/powerpc/init-first.c	2012-06-25 09:44:20.067041483 +1000
@@ -26,6 +26,7 @@ void *__vdso_gettimeofday attribute_hidd
 void *__vdso_clock_gettime;
 void *__vdso_clock_getres;
 void *__vdso_get_tbfreq;
+void *__vdso_getcpu;
 
 
 static inline void
@@ -40,6 +41,8 @@ _libc_vdso_platform_setup (void)
   __vdso_clock_getres = _dl_vdso_vsym ("__kernel_clock_getres", &linux2615);
 
   __vdso_get_tbfreq = _dl_vdso_vsym ("__kernel_get_tbfreq", &linux2615);
+
+  __vdso_getcpu = _dl_vdso_vsym ("__kernel_getcpu", &linux2615);
 }
 
 # define VDSO_SETUP _libc_vdso_platform_setup


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